Micropropagation of Pieris floribunda

Abstract

Abstract Shoot tips excised from actively growing stock plants of Pieris floribunda (Pursh ex Sims) Benth. and Hook. (mountain andromeda) in the adult growth phase, were surface disinfested, the terminal portions removed (decapitated), and the shoots placed horizontally on agar-solidified Woody Plant Medium (WPM) supplemented with 8 ppm 6-(γ,γ-dimethylallylamino)-purine (2iP), 80 ppm adenine hemisulfate, and 200 ppm NaH2PO4. Within 1 month, multiple shoot formation began and axillary shoots were excised from the original explants. These shoots were decapitated and placed on WPM with the aforementioned supplements. After 3 subcultures and 3 transfers (6 months), eight-node axillary shoots were excised, decapitated, and cultured on agar-solidified WPM supplemented with 0, 0.5, 1, 2, 4, 8, or 16 ppm 2iP. The greatest number of microcuttings ≥ 20 mm (0.8 in) having low hyperhydricity and moderate dry weight was produced at 4 ppm 2iP. Attempts at ex vitro rooting were unsuccessful and rooting was accomplished in vitro. In vitro rooting of microcuttings was optimal (75% rooting) when placed in WPM containing 15 ppm of the potassium (K) salt of 1H-indole-3-butyric acid (K-IBA) for 10 days followed by transfer to WPM lacking K-IBA. Rooted microcuttings were placed in a plug tray containing a sterile medium of 1 peat: 1 vermiculite (v/v) and transferred to high humidity (> 80% RH) for acclimatization. After 2 weeks under high humidity, plantlets were transferred to a glasshouse resulting in 49% survival.